In recent years, recording apparatuses and recording media for recording information digitally are spreading. Since, for example, image and music data are recorded and reproduced with no deterioration in these recording apparatuses and recording media, the data can be copied repeatedly with the quality of the data maintained. From the viewpoint of copyright holders, however, there is a risk that the data the copyright of which they hold may be repeatedly and fraudulently copied with their quality maintained and distributed in the market. For this reason, it is necessary on the side of recording apparatuses and recording media to take appropriate measures to prevent copyrighted data from being fraudulently copied.
As a system for such copyright protection, in the minidisc (MD) (trademark) system for example a method called SCMS (Serial Copy Management System) is used. This means information transmitted through a digital interface together with music data. This information shows under which of three types of data the music data contained fall: data for free copy, data copy once allowed or data copy prohibited. Upon receiving music data from the digital interface, a minidisc recorder detects an SCMS, and if it is copy prohibited, the music data are not recorded on the minidisc, and if it is copy once allowed, it is changed into copy prohibited and is recorded together with the music data received, and if it is copy free, it is recorded as it is together with the music data received.
In this way, in the minidisc system, the SCMS is used to prevent any fraudulent copy of copyrighted data.
Another method of preventing fraudulent copies of copyrighted data is a contents scramble system used in the Digital Versatile Disc (DVD) (trademark). In this system, all the copyrighted data on a disc are enciphered and only licenced recording apparatuses are given cipher keys which enable them to decipher and obtain meaningful data. And recording apparatuses are designed to ensure that all the operators observe the operation rules of not making fraudulent copies. In this way, the DVD system prevents copyrighted data from being fraudulently copied.
However, according to the system adopted by the minidisc system, there is a risk that recording apparatuses that do not follow the operating rule of changing the copy once allowed for the SCMS to the copy prohibited and recording the data received may be manufactured illegally.
And although the system used by the DVD system is effective in ROM media, it is not effective in RAM media in which users can record data. This is because even in cases where unauthorized persons cannot decode the encryption, an illegal copy of the whole data on the disc into a new disc can produce a new disc that works on a licensed legitimate recording apparatus.
Therefore, in the Japanese Patent Application 10-25310 (Japanese Patent Application 1999-224461 Laid Open on Aug. 17, 1999), information for identifying individual recording medium (hereinafter referred to as “medium identification information”) are inscribed in it, and this information can only be accessed by licensed apparatuses. In other words, the data on each recording medium are enciphered by a medium identification information and a key based on a secret obtained by taking a license, and apparatuses that have not obtained license cannot decode the data that they may have read making such data meaningless. Furthermore, when a license is given to an apparatus, its operation is prescribed so that no fraudulent copy may be made. Unlicensed apparatuses cannot access medium identification information, and since medium identification information varies for each medium, even if a copy may be made by an unlicensed apparatus of all information accessible to it on a new medium, such new medium enables neither unlicensed apparatuses or licensed apparatuses to read information properly.
Meanwhile, the recording apparatus according to the Patent Application includes for example an interface IEEE1394 capable of transmitting and receiving data to and from other apparatuses and may record contents data transmitted from other apparatuses on a recording medium.
In such a case, the contents data may be enciphered and transmitted by means of the Digital Transmission Content Protection Standard developed by Sony, Matsushita, Hitachi, Toshiba and Intel (this standard itself cannot be viewed without obtaining a license, but anybody can obtain a White Paper describing its outline from its licensing organization: Digital Transmission Licensing Administrator (DTLA)). The contents data are enciphered by means of a contents key Kc to be transmitted and the contents key Kc itself is enciphered. Such a safe method is used for transmission to the recording apparatuses. The simplest method for the recording apparatus to record on a recording medium the transmitted data safely, that is, without any fraudulent copy allowed is to record the contents data enciphered and transmitted as they are on the recording medium, and to encipher the contents key used for enciphering these data by means of the method used in this recording system and to record the same on the recording medium.
In this way, all that a recording apparatus must do at the time of recording is to simply receive and record a large volume of contents data, and the whole operation is simplified.
However, by the method described above, the contents data remain enciphered while they are transmitted to a recording apparatus and recorded on a medium, making the reproduction operation inconvenient.
In other words, essentially at the time of reproducing AV contents, in order to perform trick plays (reproduction while performing a quick traverse or a quick return), the format and structure of the contents data must be identified and it is to be decided which data of the recording medium should be read in response thereto.
However, in the method described above, it is impossible to identify which data are recorded in which unit of the recording medium unless the contents data are read out from the recording medium and decoded, and therefore to finely control trick plays.